This invention relates to watthour meters. In particular, the invention is directed to preventing the tampering with a meter thereby leading to the theft of electrical energy.
A problem which besets utility companies is the theft of energy achieved by meter tampering. One manner of stealing electricity is to reorientate a wattmeter to cause it to run backwards, thereby causing deregistration of energy usage. This reorientation requires that the meter be removed from its upright position in its socket and thereafter be reinstalled in an inverted position. Electric power service is maintained through the inverted meter and a rotating metering movement in the meter. The metering movement is rotated in the reverse direction because the line conductors are connected in reverse through the meter during this physical reorientation. Consequently, as electricity is used, the meter dials are driven reversedly indicating reduced consumption, when in fact, electrical energy is actually being consumed. This reverse rotation of the metering movement in the inverted position is caused due to the reverse connection of the meter windings across the line conductors, thereby causing a phase reversal in the winding magnetic field driving the metering movement. With the increasing expense of energy, this thieving is becoming of a more serious nature.
One known method of overcoming the orientation, as described in U.S. Pat. Nos. 4,034,290 (Warren) and 4,104,588 (Westberry) is to provide mating the meter mounting means and socket combinations that permit a meter to be plugged into the socket in such an orientation only. This is economical only in new installations because of the expenses involved in removing standard meter installations and the replacement with newly designed meters.
Another known means is a "red flag" indicator used to show that a meter has been stopped as shown in U.S. Pat. No. 3,915,112. A problem with such a meter is that during shipping, the indicator can be tripped with the result that the meter seal must be broken and the cover removed to reset the flag before the meter can be operated. The cover seal is the manufacturer's guarantee of accuracy of the meter and when broken, the meter must be retested before it can be resealed. This would result in additional time and expense.
U.S. Pat. No. 4,039,943 (Tapscott) discloses a gravity actuated switch for reversing the meter voltage winding connections when a meter is inverted thereby retaining the same rotational movement of the metering movement. Such a meter is relatively complex and accordingly expensive. Reference is made in Tapscott (column 1, line 38-45) to a meter by Westinghouse Electric Corporation style number 285 A 082 G02 employing a detent assembly to prevent meter movement rotation in reverse. Such a device is mechanically linked to the motor assembly and is responsive to motor operation and is hence relatively complex and accordingly expensive.
In view of this, there is a need for an economical anti-theft meter which does not have encumbent in it the problems with devices known in the art, and which is yet reliable in operation, which can be supplied to new meters and also retrofitted to installed meters.